The present invention relates generally to a swash plate compressor and more particularly to improvements to such a compressor so that the size, energy consumption, and vibrational characteristics are minimized.
Conventional swash plate compressors utilize a rotating swash plate, driven by a drive shaft, to drive a piston. The piston is used to transfer fluid from the low pressure side of an air conditioning system or other device to the high pressure side. Conventional swash plate compressors utilize an elbow to transfer the rotational drive of the drive shaft to the swash plate. The utilization of an elbow, or similar mechanism, to transfer the rotational drive of the drive shaft has several undesirable characteristics. This conventional design transfers undesirable stresses to the swash plate requiring the swash plate to be designed for a higher strength. This adds to the size, weight, and cost of the swash plate compressor. The presence alone of the elbow or similar mechanism adds to the size, weight, complexity and manufacturing cost of the conventional swash plate compressor. In addition, the elbow, as it rotates with the drive shaft, limits the potential travel distance of the piston. The presence of the elbow additionally prevents the use of a double-sided piston to provide pumping action in both directions of piston travel.
It is known that varying the angle of the swash plate relative to the drive shaft allows the swash plate compressor to produce variable fluid transfer rates. One known design utilizes a biasing spring and the crankcase pressure within the compressor to vary the angle of the swash plate. This crankcase pressure can lead to undesirable stresses on the swash plate and can have a negative effect on the vibrational characteristics of the swash plate compressor.
Finally, the piston driving mechanisms in known variable swash plate compressors utilize multiple pivot locations. The swash plate itself typically slides and/or rotates axially on the drive shaft, the elbow joint slides and/or rotates about a pin in the elbow, and the piston joint rotates about its connection with the swash plate. The position and rotation of the swash plate, the elbow, and the piston in relation to each pivot location controls the path of the piston. These multiple pivot locations often result in a variable Top-Dead-Center (xe2x80x9cTDCxe2x80x9d) of the piston. The TDC of the piston is the distance between the piston face and the piston chamber outlet face at the top of the piston cycle. Variations in the piston TDC result in undesirable variations in the variable swash plate compressor""s output.
Therefore, there is a need for a variable swash plate compressor design that reduces the stresses in the swash plate, allows for greater piston travel without increasing the compressor size, (allows for double-sided pistons), reduces undesirable vibrational characteristics, reduces variation in piston TDC, and reduces the size, weight, and manufacturing cost of known variable swash plate compressor designs.
It is therefore an object of the present invention to provide a variable swash plate compressor that reduces the stress in the swash plate, reduces vibrations in the compressor, and reduces the variation in piston TDC. It is a further object of the present invention to provide a variable swash plate compressor that doubles the output of a given size compressor through the use of double-sided pistons. It is a further object of the present invention to provide a variable swash plate compressor that reduces the size, weight, and manufacturing costs associated with conventional swash plate compressor design.
In accordance with the objects of this invention, a variable swash plate compressor is provided. The variable swash plate compressor includes a housing, a drive shaft and a control surface element. The control surface element is attached to and receives a rotational drive force from the drive shaft. The control surface element has a pinnacle element attached thereto.
The variable swash plate compressor also includes a swash plate with a bore located in its center. The control surface element sits within the bore of the swash plate. The swash plate also includes a pocket in which the pinnacle element is seated. The drive shaft transmits a rotational drive force to the swash plate through the control surface element seated in the bore of the swash plate and the pinnacle element seated in the swash plate pocket.
The variable swash plate compressor also includes a double-sided compression piston positioned within a piston chamber formed in the housing. As the double-sided compression piston moves within the piston chamber it alternates between simultaneously drawing fluid into the bottom of the piston chamber through a bottom inlet while forcing fluid within the top of the piston chamber out of the top outlet and simultaneously drawing fluid into the top of the piston chamber through a top inlet while forcing fluid within the bottom of the piston chamber out of the bottom outlet. The double-sided compression piston is moved in this cyclical fashion by remaining in contact with the rotating swash plate such that only axial forces are transmitted between the swash plate and the double-sided compression piston. As the angle between the swash plate and the drive shaft is increased, the travel path of the double-sided compression piston is increased resulting in an increase in the output of the variable swash plate compressor.
The variable swash plate compressor also includes a fulcrum piston assembly for controlling the angle of the swash plate relative to the drive shaft. As the angle of the swash plate relative to the drive shaft is increased, the output of the variable swash plate compressor is increased. The fulcrum piston assembly changes the angle of the swash plate by exerting a force on the swash plate causing it to pivot about the tip of the pinnacle element. The tip of the pinnacle element orbits the axial center of the drive shaft at a distance equal to the distance from the center of the drive shaft to the axial center of the double-sided compression piston. By pivoting the swash plate about a point that orbits over the axial center of the double-sided compression piston, variation in the TDC of the double-sided compression piston is reduced.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.